It is well known that 1-olefins can be polymerized either alone or in combinations of two or more with catalysts containing chromium compounds. The oldest and probably the most well known is the Phillips catalyst made by extending a water soluble chromium compound like chromium trioxide, ammonium chromate, etc. onto an inorganic oxide support like silica, alumina, zirconia, thoria, etc. In U.S. Pat. No. 3,780,011, assigned to the assignee hereof, there is described a catalyst containing titanium on chromium trioxide-silica which gives higher activity, higher melt index and higher HLMI/MI for the polymer and also no induction time in ethylene polymerization as contrasted to the conventional Phillips catalyst. Recently Union Carbide Corp. obtained U.S. Pat. Nos. 3,806,500; 3,844,975; 3,709,853; 3,756,998; 3,324,101; 3,642,749; 3,836,595; 3,687,920, etc. in which chromium compounds like organosilyl chromate, pi-bonded allyl chromium, cyclopentadienyl chromium, etc. when extended onto inorganic supports like silica showed catalytic activity for ethylene polymerization.
In U.S. Pat. Nos. 3,884,832 and 3,941,761, both assigned to the assignee hereof, there is described a novel catalyst system and method for the polymerization of olefins. An organotin chromate compound when supported on silica or the like modified with the metals titanium, zirconium, etc. and with an alkyl aluminum compound gave a highly active ethylene polymerization catalyst. The polymers produced are ultra high molecular weight and are useful in forming very tough and abrasion resistant articles like gears, coal mine chutes, etc.